1. Field of the Invention
The present invention relates to a bridge apparatus and a bridge system.
2. Description of the Related Art
Home networking at general home has been progressed with rapid prevalence of personal computers and broadband systems. Up to now, a primary object of a home network has been limited to connection between a personal computer and peripheral devices such as a broadband router or a printer. In recent years, white goods and AV equipment as well as a personal computer have been equipped with network connection functions, and become constituent elements of a home network. Digital home electronics having this communication function, called information home electronics, provide a new function to a user by making connection to the Internet or providing an access to another equipment.
However, at present, transparent interconnection between these items of equipment (a personal computer and its peripheral devices, white goods, or AV equipment) configuring a home network is not achieved. This problem is caused by the fact that a control protocol for interconnecting personal computers and information home electronics with each other is not commonly shared. Currently, a plurality of control protocols coexist over a home network. The control protocols targeted for use in a home network can include AV/C utilized on a high speed IEEE1394 serial bus and ECHONET (registered trademark) available over a variety of communication networks.
UPnP is provided as an internationally standardized protocol whose main purpose is to interconnect personal computers and their peripheral devices or network devices such as routers, and utilizes a TCP/IP network constructed over Institute of Electrical and Electronics (IEEE) network 802. At present, its target is extended to AV equipment, and its standardization is in progress.
The high speed IEEE1394 bus network is targeted for use in AV equipment, and AV/C utilized over this network is a protocol standard for transmitting and receiving control commands of the AV equipment.
ECHONET is provided as a Japanese standard for control protocols targeted for use in white goods, sensors, and facilities. ECHONET is assumed to be used over a variety of communication networks such as IEEE802, Bluetooth (registered trademark), an infrared system, an electric line, and low power radio.
The UPnP, AV/C, and ECHONET are provided as incompatible, independent protocol standards, and an available communication network is different for each standard except that both UPnP and ECHONET operate over the IEEE802 network. Therefore, equipment conforming to one control protocol cannot control equipment conforming to another protocol. For example, a personal computer conforming to UPnP cannot control an air conditioner conforming to ECHONET or a video recorder conforming to an AV/C protocol.
A bridge apparatus solves this problem and enables equipment conforming to one protocol to control equipment conforming to another protocol. The bridge apparatus is interposed in a network used by both protocols, and converts one protocol to another protocol. At this time, in the case where one protocol has a mechanism for searching and disclosing equipment information and information on functions provided in the equipment, it is a problem how items of information of equipment belonging to another protocol are disclosed to the former protocol. A variety of solutions to this problem have been proposed. For example, in JP-A 2003-8610 (KOKAI), there is described a technique of making IEEE1394 equipment operable using an UPnP protocol by converting an AV/C command utilized over an IEEE1394 packet or the IEEE1394 network into a simple object access protocol (SOAP) message. In this document, there has been proposed a solution as to how functions provided in the IEEE1394 equipment are expressed as the UPnP equipment functions. Basically, this solution is featured in that the IEEE1394 equipment is virtually seen as UPnP equipment (hereinafter, referred to as a virtual UPnP) on a bridge apparatus.
However, this document fails to mention a problem occurring in the case where the IEEE1394 equipment targeted for use in bridging (hereinafter, referred to as a “source device”) is powered OFF or in the case where an IEEE1394 cable is disconnected and no access can be provided to the source device via the IEEE1394 network. In the case where a bridge apparatus cannot access the source device via the IEEE1394 network, an UPnP control point over the UPnP network to which a bridge has been connected cannot access the source device, either. Current home electronics equipment with advanced low power consumption automatically moves to a suspended state if a user does not operate for a predetermined period of time. Thus, an access through a network via the bridge apparatus is limited to a limited period after the user has physically operated the source device.
This feature is particularly significant in white goods. In washing machines or microwaves, when washing or cooking is completed by a user's operation, power is usually turned off immediately. Although an advantage of operating home electronics equipment by utilizing a network is that an access can be provided anytime and anywhere, this advantage cannot be utilized by an energy saving mechanism of the source device.
In addition, a general problem occurring regardless of whether or not a gateway is interposed is that an UPnP control point cannot send a control command unless an UPnP device targeted for control is communicable. Thus, the UPnP control point needs to take an implementation mode for sending a control command after it has been determined whether communication with the target is enabled or disabled. As described previously, in the case where home electronics equipment frequently moves to a power saving mode, disabling communication, there is a possibility that an amount of time during which control can be achieved from the UPnP control point via a network is very small.
The bridge apparatus disclosed in the above document does not consider support for home electronics equipment with a power saving mode that frequently moves to a suspended state, and thus, an access can be provided via the bridge apparatus, namely, via a network for only a predetermined period limited after the user has operated the source device via a physical interface. Essentially, the bridge apparatus disclosed in the above document is targeted for use in AV equipment based on the IEEE1394, not for white goods (ECHONET compatible equipment) that often automatically move to such a suspended state.